Re: Linux Kernel 5.7.9 DRM Double Free

[Greg KH <greg () kroah com>]

On Wed, Aug 19, 2020 at 03:42:33PM +0000, zdi-disclosures () trendmicro com wrote:
> The specific flaw exists within DRM memory management. The issue results from the lack of validating the existence of 
> an object prior to performing operations on the object. An attacker can leverage this vulnerability to escalate 
> privileges and execute code in the context of the kernel.

Note, this "vulnerability" was only accessible by root, so there's not
all that many privileges that could really be escalated there.  Don't
know why the original poster did not say that here, as they acknowledged
it in the "bug report" they sent many of us.

> This has been already addressed in the upstream commit 5de5b6ecf97a021f29403aa272cb4e03318ef586

It was already "addressed" before this problem was pointed out to
anyone, so this was not fixed in relation to this being reported.

Also, the fix is now in the 4.19.140, 5.4.59, 5.7.16, 5.8.2 kernel
releases for those that care.

And finally, it was pointed out that any kernel running with the
CONFIG_SLAB_FREELIST_HARDENED=y option would not have any problems with
this issue before it was fixed.

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thanks,

greg k-h